How do I stretch my object from one point to the other?
I think you can solve this with snapping and transforms with cursor as pivot. I tried to rebuild a situation similar to what I see in your picture, so that the truss is of different size and rotation than the other shape:



First of all, switch to top view, and activate vertex snapping like below:



Then, translate the truss towards the other shape, and snap a corner vertex as below:



Then, go into edit mode (of the truss) and select one corner vertex, then snap the 3D cursor to it.



Now you can activate cursor pivoting, and rotate the truss



...until its upper vertex snaps to the other shape, perfectly:



Now the different angle is gone, and you can switch to front view, to stretch (scaling) the truss until it matches (snapping) the other shape perfectly:



Does this solve your issue?